The long-range objective of this research is to determine the number, function and regulation of the I (Immune response) region genes of the H-2 gene complex. The I region genes control numerous traits which are important to research on transplantation, viral oncogenesis, disease resistance and the cellular interactions leading to immune surveillance, immune response and immune suppression. The detection of intra-H-2 recombinants and identification of I region associated antigens have greatly facilitated the elucidation and resolution of this chromosomal segment. Yet, we need more recombinants and analytical tools to further decipher these genes. The immediate objectives of the proposed research are: (1) screen specifically for I region recombinants and mutants; 2) identify the I region genes in mice from several sources; 3) further dissect the I region function with several in-vitro and in-vivo techniques; 4) explore the role of I region genes in leukemogenesis; 5) to initiate collaborative arrangements to further define the structural and functional aspects of I region products.